1. Field of the Invention
The present invention relates to a novel hydrogenated ring-opening metathesis polymer and, more particularly, to a hydrogenated ring-opening metathesis polymer, which is superior in heat resistance, pyrolysis resistance and light transmission properties and which is suited for use as a photoresist polymer for microlithography by ultraviolet and far ultraviolet lights (including excimer lasers) in the production of semiconductor devices, and a method of producing the hydrogenated polymer.
2. Description of the Related Art
With the recent increase of integration level in integrated circuits on semiconductor devices, a large-scale integrated circuit (LSI) and a very-large-scale integrated circuit (VLSI) have been put to practical use and, at the same time, a minimum lithographic pattern in the integrated circuits would be reaching in sub-micron features, in future, it tends to be more microlithographic. In the formation of the microlithographic pattern, there is essentially required to use a lithography technique of coating a surface of a substrate with a resist material to form a thin film, selectively exposing the resulting resist film to light thereby to form a latent image of a desired pattern, developing the latent image to form a resist pattern, performing dry etching using this resist pattern as a mask, and removing the resist to obtain a desired pattern.
As an exposure light source used in this lithographic technique, for example, ultraviolet lights of g-lines (wavelength: 436 nm) or i-lines (wavelength: 365 nm) have been used. With the progress of the fine lithographic pattern, it has become popular to use an exposure light having a shorter wavelength such as far ultraviolet lights, vacuum ultraviolet lights, electron beams (EB) and X-rays as the light source. As the exposure light source, excimer laser (e.g. KrF laser having a wavelength of 248 nm, ArF laser having a wavelength of 193 nm, etc.) has attracted special interest recently and it is expected that the excimer laser is effective for formation of the fine lithographic pattern.
As a polymer or copolymer used as a resist material for formation of a sub-micron pattern using exposure light having a shorter wavelength within a vacuum ultraviolet region, for example, there have been suggested various polymers and copolymers, such as polymer or copolymer of an acrylic or xcex1-substituted acrylic ester having an adamantane skeleton and an acid cleavable protecting group at an ester portion (see Japanese Patent Kokai Publication No. 39665/1992), polymer or copolymer of an acrylic or xcex1-substituted acrylic ester having a norbornane skeleton and an acid cleavable protecting group at an ester portion (see Japanese Patent Kokai Publication No. 257281/1993), polymer or copolymer of cyclohexylmaleimide (see Japanese Patent Kokai Publication No. 257285/1993), polymer compound containing a cellulose skeleton in a principal chain, said principal chain being cleaved by an acid (see Japanese Patent Kokai Publication No. 342212/1994), polyvinyl alcohol or its derivative (see Japanese Patent Kokai Publication No. 333850/1995) and the like.
However, there have still not been obtained polymers and copolymers, which satisfy all of various properties required to be used as the polymer for the resist material, such as dry etching resistance, transparency to far ultraviolet lights, solubility in resist solvent, wettability by developer, adhesion to substrate such as silicon, solubility in releasant and the like, and a further development thereof is required.
On the other hand, a cyclic polymer in a photoresist composition (WO97/33198) comprising a polymer compound having an aliphatic cyclic hydrocarbon as a principal chain and containing pendant acid cleavable groups is superior in dry etching resistance and also superior in transparency to far ultraviolet lights. However, it had a problem that the solubility in resist solvent in high concentration, wettability by developer and adhesion to silicon substrate are inferior.
An object of the present invention is to provide a hydrogenated ring-opening metathesis polymer, which satisfy all of the above various properties required to be used as a polymer for the resist material and also has a narrow molecular weight distribution, and to provide a method of producing the hydrogenated polymer.
Another object of the present invention to provide a resist material using the hydrogenated polymer, which is superior in dry etching resistance, transparency to far ultraviolet lights, solubility in resist solvent, wettability by developer, adhesion to substrate such as silicon, and solubility in releasant.
To solve the above problems, the present inventors have studied intensively about a possibility of using a hydrogenated ring-opening metathesis polymer obtained from a cyclic olefinic monomer or monomers as a polymer for resist material having excellent optical characteristics, electrical characteristics, high rigidity, heat resistance, adhesion to substrate and weathering resistance. As a result, they have found that a novel hydrogenated ring-opening metathesis polymer satisfies various performances as the resist material, thus completing the present invention.
That is, the present invention provides:
(i) A hydrogenated ring-opening metathesis polymer comprising at least a structural unit (A) represented by the following general formula (1): 
wherein at least one of R1 to R4 is a substituent containing an acid cleavable group, and others are selected from hydrogen, an alkyl group having 1 to 20 carbon atoms, a halogen, a halogenated alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20 carbon atoms, an alkylcarbonyloxy group having 2 to 20 carbon atoms, an arylcarbonyloxy group having 7 to 20 carbon atoms, an alkylsulfonyloxy group having 1 to 20 carbon atoms, an arylsulfonyloxy group having 6 to 20 carbon atoms, a carboxy group, a hydroxy group, a carboxyalkyl group having 2 to 20 carbon atoms, or a hydroxyalkyl group having 1 to 20 carbon atoms; X1 is selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR5xe2x80x94, xe2x80x94PR5xe2x80x94 or xe2x80x94CR52xe2x80x94 (R5 represents hydrogen or an alkyl group having 1 to 20 carbon atoms) and may be the same or different; and m represents 0 or an integer of 1 to 3; a structural unit (B) represented by the following general formula (2): 
wherein at least one of R6 to R9 is a substituent containing carboxy or hydroxy, and others are selected from hydrogen, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a halogen, a halogenated alkyl group having 1 to 20 carbon atoms, an alkylcarbonyloxy group having 2 to 20 carbon atoms, an arylcarbonyloxy group having 7 to 20 carbon atoms, an alkylsulfonyloxy group having 1 to 20 carbon atoms, or an arylsulfonyloxy group having 6 to 20 carbon atoms; X2 is selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR10xe2x80x94, xe2x80x94PR10xe2x80x94 or xe2x80x94CR102xe2x80x94 (R10 represents hydrogen or an alkyl group having 1 to 20 carbon atoms) and may be the same or different; and n represents 0 or an integer of 1 to 3; and a structural unit (C) represented by the following general formula (3): 
wherein at least one of R11 to R14 is a substituent containing cyano or lactonyloxycarbonyl, and others are selected from hydrogen, a carboxy group, a hydroxy group, a carboxyalkyl group having 2 to 20 carbon atoms, a hydroxyalkyl group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonylalkyl group having 3 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a halogen, or a halogenated alkyl group having 1 to 20 carbon atoms; X3 is selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR15xe2x80x94, xe2x80x94PR15xe2x80x94 or xe2x80x94CR152xe2x80x94 (R15 represents hydrogen or an alkyl group having 1 to 20 carbon atoms) and may be the same or different; and 1 represents 0 or an integer of 1 to 3,
wherein a constituent molar ratio of the structural unit (A)/(B) is from 1/99 to 99/1 and a constituent molar ratio of the structural unit (B)/(C) is from 30/70 to 100/0 and, furthermore, a ratio of a weight-average molecular weight Mw to a number-average molecular weight Mn, that is Mw/Mn is from 1.0 to 2.0.
The present invention also provides:
(ii) A method of producing a hydrogenated ring-opening metathesis polymer, which comprises polymerizing at least one cyclic olefinic monomer represented by the general formula (4), or at least two cyclic olefinic monomers represented by the general formulas (4) and (5), or at least three cyclic olefinic monomers represented by the general formulas (4), (5) and (6) using a living ring-opening metathesis catalyst, and hydrogenating the polymer in the presence of a hydrogenation catalyst.
General formula (4) being: 
wherein at least one of R16 to R19 is a substituent containing an acid cleavable group, and others are selected from hydrogen, an alkyl group having 1 to 20 carbon atoms, a halogen, a halogenated alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20 carbon atoms, an alkylcarbonyloxy group having 2 to 20 carbon atoms, an arylcarbonyloxy group having 7 to 20 carbon atoms, an alkylsulfonyloxy group having 1 to 20 carbon atoms, or an arylsulfonyloxy group having 6 to 20 carbon atoms; X4 is selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR20xe2x80x94, xe2x80x94PR20xe2x80x94 or xe2x80x94CR202xe2x80x94 (R20 represents hydrogen or an alkyl group having 1 to 20 carbon atoms) and may be the same or different; and x represents 0 or an integer of 1 to 3.
General formula (5) being: 
wherein at least one of R21 to R24 is a carboxy group, a hydroxy group, a carboxyalkyl group having 2 to 20 carbon atoms, a hydroxyalkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20 carbon atoms, an alkylcarbonyloxy group having 2 to 20 carbon atoms, an ma arylcarbonyloxy group having 7 to 20 carbon atoms, an alkylsulfonyloxy group having 1 to 20 carbon atoms, an arylsulfonyloxy group having 6 to 20 carbon atoms, or a carboxylic anhydride formed from R21 and R23 of R21 to R24, and others are selected from hydrogen, an alkyl group having 1 to 20 carbon atoms, a halogen or a halogenated alkyl group having 1 to 20 carbon atoms; X5 is selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR25xe2x80x94, xe2x80x94PR25xe2x80x94 or xe2x80x94CR252xe2x80x94 (R25 represents hydrogen or an alkyl group having 1 to 20 carbon atoms) and may be the same or different; and y represents 0 or an integer of 1 to 3.
General formula (6) being: 
wherein at least one of R26 to R29 is a substituent containing cyano or lactonyloxycarbonyl, and others are selected from hydrogen, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonylalkyl group having 3 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a halogen, or a halogenated alkyl group having 1 to 20 carbon atoms; X6 is selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR30xe2x80x94, xe2x80x94PR30xe2x80x94 or xe2x80x94CR302xe2x80x94 (R30 represents hydrogen or an alkyl group having 1 to 20 carbon atoms) and may be the same or different; and z represents 0 or an integer of 1 to 3.
(iii) A method of producing a hydrogenated ring-opening metathesis polymer of (ii), wherein the substituent is further converted into a new substituent containing an acid cleavable group after hydrogenation.
(iv) A method of producing a hydrogenated ring-opening metathesis polymer of (ii), wherein hydrolysis is further conducted after hydrogenation.
(v) A method of producing a hydrogenated ring-opening metathesis polymer of (ii), wherein hydrolysis is conducted after hydrogenation and the substituent is further converted into a new substituent containing an acid cleavable group after hydrogenation.
(vi) A method of producing a hydrogenated ring-opening metathesis polymer, wherein at least one cyclic olefinic monomer represented by the general formula (4), or at least two cyclic olefinic monomers represented by the general formulas (4) and (5), or at least three cyclic olefinic monomers represented by the general formulas (4), (5) and (6) is/are polymerized by using a living ring-opening metathesis catalyst in the presence of an olefin or diene.
The present invention also provides (vii) a base polymer for photoresist, comprising a hydrogenated ring-opening metathesis polymer of (i).
The hydrogenated ring-opening metathesis polymer for photoresist according to the present invention is a polymer, which is superior in adhesion, heat resistance, pyrolysis resistance and light transmission properties and which is suited for use as a photoresist polymer for microlithography by ultraviolet and far ultraviolet lights in the production of semiconductor devices, and is of a great value from an industrial point of view. According to the present invention, there can be provided a method of producing such a useful hydrogenated ring-opening metathesis polymer, efficiently and easily.